Paper feed roller

ABSTRACT

A paper feed roller that can prevent paper sheet transport failure caused by accumulation of paper powder for a long period of time is provide. This paper feed roller includes a shaft body and an elastic body layer formed on the outer periphery of the shaft body. Unevenness are formed by protrusions on the circumferential surface of the elastic body layer. The protrusions are arranged on the circumferential surface of the elastic body layer in a direction different from an axial direction. The gap between a row of protrusions which extends in the direction different from the axial direction and a row of protrusions which is parallel to the row of protrusions is a continuous recess, i.e., a groove, and the width of the groove is greater than the distance between the protrusions in the row of protrusions which extends in the direction different from the axial direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of International Application number PCT/JP2018/028573, filed on Jul. 31, 2018, which claims the priority benefit of Japan Patent Application No. 2017-166590, filed on Aug. 31, 2017 and Japan Patent Application No. 2017-190262, filed on Sep. 29, 2017. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND Technical Field

The disclosure relates to a paper feed roller that is used in an exemplary embodiment in electrophotographic equipment that employs an electrophotographic method such as a copier, a printer, or a facsimile.

Background Art

A paper feed roller is formed in a cylindrical shape, for example, by an elastic material such as a rubber crosslinked body, and a circumferential surface thereof serves as a contact surface with paper sheets. Paper powder generated from the paper sheets may adhere to the circumferential surface of the paper feed roller. In addition, the paper powder may accumulate on the circumferential surface of the paper feed roller while the surface repeatedly comes in contact with the paper sheets. If paper powder accumulates, a contact area of the circumferential surface with the paper sheet decreases, and thus a coefficient of friction of the contact surface with the paper sheets becomes smaller. As a result, paper sheet transport failure may occur.

A paper feed roller in which unevenness are formed on a circumferential surface to reduce paper sheet transport failure is known (Patent Literature 1 and 2, etc.). For example, Patent Literature 1 discloses a paper feed roller in which a plurality of ridges and grooves are formed in parallel to the axial direction. In addition, Patent Literature 2 discloses a paper feed roller in which embossments are formed on a circumferential surface.

[Patent Literature 1]

Japanese Laid-Open No. 2003-112833

[Patent Literature 2]

Japanese Laid-Open No. 2000-296937

There is no conventional paper feed roller that sufficiently mitigates accumulation of paper powder and maintains a satisfactory coefficient of friction for a long period of time from an initial stage of use. In particular, paper sheets that have been used in recent years include paper sheets with low quality, and such paper sheets with low quality are likely to generate paper powder and are likely to cause paper sheet transport failure in a relatively early stage.

SUMMARY OF DISCLOSURE

A paper feed roller according to the disclosure includes a shaft body and an elastic body layer formed on an outer periphery of the shaft body, in which unevenness are formed by protrusions on an circumferential surface of the elastic body layer, the protrusions are arranged on the circumferential surface of the elastic body layer in a direction different from an axial direction, grooves that are continuous recesses are formed between rows of protrusions that extend in a direction different from the axial direction and rows of protrusions that are parallel to the rows of the protrusions, and a width of one of the grooves is larger than a protrusion separation distance in the row of protrusions.

The protrusions may be hemispherical protrusions. The protrusions may be arranged on the circumferential surface of the elastic body layer in a direction different from a circumferential direction. In this case, the protrusions may be arranged on the circumferential surface of the elastic body layer in a spiral shape. In addition, the protrusions may be arranged on the circumferential surface of the elastic body layer in a direction at an angle of +10° or less with respect to the circumferential direction. In addition, the protrusions may be arranged on the circumferential surface of the elastic body layer in the circumferential direction.

The protrusion separation distance in the row of protrusions may be in a range of 0 to 0.6 mm. The width of one of the grooves may be in a range of 0.01 to 2.0 mm. A height of one of the protrusions may be in a range of 0.05 to 0.5 mm. A curvature radius of one of the protrusions may be in a range of 0.05 to 1.0 mm. A pitch of the grooves may be in a range of 0.1 to 2.0 mm.

The protrusions may be spherical segment-shaped protrusions. An upper bottom of one of the spherical segment-shaped protrusion may be a polished surface. An upper bottom of one of the spherical segment-shaped protrusion may be a plane. An upper bottom of one of the spherical segment-shaped protrusion may be a curved surface having a larger curvature radius than a spherical zone of the spherical segment-shaped protrusion. A ratio of a diameter r1 of the upper bottom to a diameter r2 of a lower bottom (r1/r2) of one of the spherical segment-shaped protrusion may be in a range of 0.50 to 0.95. The angle formed by a tangent of a spherical zone of one of the spherical segment-shaped protrusions at an intersection point of the spherical zone with the upper bottom of the spherical segment-shaped protrusion may be in a range of 100 to 150°. A height of the spherical segment-shaped protrusion may be in a range of 0.02 to 0.40 mm.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an external appearance of a paper feed roller according to an embodiment of the disclosure.

FIG. 2(a) illustrates an enlarged schematic diagram of a circumferential surface of the paper feed roller illustrated in FIG. 1 and FIG. 2(b) illustrates an A-A line cross-sectional diagram thereof.

FIGS. 3(a) and 3(b) illustrate enlarged cross-sectional schematic diagrams of a protrusion of the paper feed roller, where FIG. 3(a) illustrates (a) a protrusion in the shape of a half of a sphere cut on a plane passing through the center of the sphere and FIG. 3(b) illustrates a protrusion in a shape smaller than the half of the sphere cut on a plane not passing through the center of the sphere.

FIG. 4 is a schematic diagram of an external appearance of a paper feed roller according to another embodiment of the disclosure.

FIG. 5 is a schematic diagram of an external appearance of a paper feed roller according to another embodiment of the disclosure.

FIG. 6 illustrates an example of a cross-sectional shape of a protrusion which is a spherical segment-shaped protrusion.

FIG. 7 illustrates an example of a cross-sectional shape of a protrusion which is a spherical segment-shaped protrusion having a polished surface.

DESCRIPTION OF EMBODIMENTS

The disclosure provides a paper feed roller that can prevent paper sheet transport failure caused by accumulation of paper powder for a long period of time.

According to the paper feed roller of the disclosure, the grooves that are continuous recesses are formed on the circumferential surface of the elastic body layer in the direction different from the axial direction by rows of protrusions arranged on the circumferential surface of the elastic body layer which extend in the direction different from the axial direction and rows of protrusions which are parallel thereto, and since the width of one of the grooves is larger than the protrusion separation distance in the row of protrusions arranged in the direction different from the axial direction, paper sheet transport failure caused by accumulation of paper powder is prevented for a long period of time. The reason for this is that paper powder generated on the protrusions, which serve as contact surfaces with paper sheets at the time of paper feed, is allowed to easily escape to the neighboring grooves from the protrusions since the width of one of the grooves is greater than the protrusion separation distance in the row of the protrusions which are arranged in the direction different from the axial direction, and paper powder is easily discharged to the outside of the roller from the grooves according to rotation of the roller without staying in the grooves since the grooves are continuous in the direction different from the axial direction.

At this time, if the protrusions are hemispherical, the contact surfaces with paper sheets are curved surfaces, and thus the generation of paper powder is relatively suppressed, and paper feed performance becomes excellent accordingly. In addition, if the protrusions are arranged on the circumferential surface of the elastic body layer in the direction different from the circumferential direction, paper powder generated on the protrusions is allowed to escape more easily to the neighboring grooves from the protrusions than when the protrusions are arranged in the circumferential direction. Accordingly, paper sheet transport failure caused by accumulation of paper powder is further prevented. In addition, if the protrusions are arranged on the circumferential surface of the elastic body layer in the direction at an angle of +10° or less with respect to the circumferential direction, paper powder generated on the protrusions is allowed to escape particularly easily to the neighboring grooves from the protrusions. In addition, the arrangement of the protrusions on the circumferential surface of the elastic body layer in the circumferential direction allows paper powder generated on the protrusions to easily escape to the neighboring grooves from the protrusions.

In addition, if the protrusion separation distance in the row of protrusions is in the range of 0 to 0.6 mm, paper powder does not easily stay in gaps between the rows of protrusions, the paper powder easily moves to the neighboring grooves, and thus the paper powder is easily discharged to the grooves. In addition, since the number of protrusions in the direction of the rows of protrusions is large, the contact area with a paper sheet increases, a load on the paper sheet is suppressed to a low level, and thus generation of paper powder is easily suppressed.

In addition, if the width of one of the grooves is in the range of 0.01 to 2.0 mm, paper powder moved to the groove does not easily clogged in the groove but is easily discharged from the groove to the outside of the roller. In addition, since the number of protrusions in the axial direction is large, the contact area with a paper sheet increases, a load on the paper sheet is suppressed to a low level, and thus generation of paper powder is easily suppressed.

In addition, if the height of one of the protrusions is in the range of 0.05 to 0.5 mm, the volume of the grooves increases, and paper powder moved to the grooves does not easily clogged in the grooves but is easily discharged from the grooves to the outside of the roller. In addition, because a size of one protrusion is suppressed to be reasonably small, a movement distance of paper powder to the grooves is suppressed to be short, and paper powder is easily discharged to the grooves.

In addition, if the curvature radius of one of the protrusions is in the range of 0.05 to 1.0 mm, the contact area with a paper sheet increases, a load on the paper sheet is suppressed to a low level, and thus generation of paper powder is easily suppressed. In addition, because a size of one of the protrusions is suppressed to be reasonably small, a movement distance of paper powder to the grooves is suppressed to be short, and paper powder is easily discharged to the grooves.

In addition, if the pitch of one of the grooves is in the range of 0.1 to 2.0 mm, the width of the groove increases, and thus paper powder moved to the groove does not easily clogged in the groove but is easily discharged from the groove to the outside of the roller. In addition, because a size of one of the protrusions is suppressed to be reasonably small, a movement distance of paper powder to the grooves is suppressed to be short, and paper powder is easily discharged to the grooves.

In addition, if one of the protrusions has a spherical segment shape, the generation of paper powder is suppressed, and paper sheet transport failure is prevented for a long period of time. In addition, if the upper bottom of the spherical segment-shaped protrusion is a polished surface, the generation of paper powder is particularly suppressed. In addition, if a ratio of the diameter r1 of the upper bottom to the diameter r2 of the lower bottom (r1/r2) of the protrusion is in the range of 0.50 to 0.95, the generation of paper powder is particularly suppressed, and paper sheet transport failure is prevented for a long period of time. In addition, if the angle formed by the tangent of a spherical zone of the protrusion with at the intersection point of the spherical zone with the upper bottom of the protrusion is in the range of 100 to 150°, the generation of paper powder is particularly suppressed, and paper sheet transport failure is prevented for a long period of time.

A paper feed roller according to the disclosure (which will also be referred to simply as a paper feed roller below) will be described in detail. FIG. 1 is a schematic diagram of an external appearance of a paper feed roller according to an embodiment of the disclosure. FIG. 2(a) illustrates an enlarged schematic diagram of a circumferential surface of the paper feed roller illustrated in FIG. 1 and FIG. 2(b) illustrates an A-A line cross-sectional diagram thereof.

The paper feed roller 10 according to the embodiment of the disclosure includes a shaft body 12 and an elastic body layer 14 which is formed on the outer periphery of the shaft body 12. The elastic body layer 14 is formed as a layer visible on a surface of the paper feed roller 10 (outermost layer). The elastic body layer 14 has a tubular shape (cylindrical shape).

Hemispherical protrusions 16 are provided on the circumferential surface of the elastic body layer 14. A recess that is lower than the protrusions 16 is formed between a protrusion 16 and a protrusion 16, and unevenness are formed by the protrusions 16 on the circumferential surface of the elastic body layer 14. A spherical shape is a substantially spherical shape, and a shape close to a spherical shape with a curved surface is possible. Spherical shapes include, for example, a true spherical shape and an elliptically spherical shape. Hemispherical shapes include the shape of a half of a sphere cut on a plane passing through the center of the sphere, and a shape larger than a half of a sphere and a shape smaller than a half of a sphere cut on a plane not passing through the center of the sphere.

The protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in a direction different from an axial direction X. Specifically, the protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in a direction at a predetermined angle θ with respect to a circumferential direction Y. In addition, the protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in a spiral shape. Further, although the protrusions 16 are also arranged on the circumferential surface of the elastic body layer 14 in the axial direction X, the protrusions 16 may not be arranged in the axial direction X.

In rows of the protrusions 16 which extend in the direction different from the axial direction X, the protrusions 16 are separated from one another by predetermined gaps a in the rows. The gap between the row of protrusions 16 extending in the direction different from the axial direction X and the row of the protrusions 16 parallel thertois grooves 18 that is continuous recess. A width b of the groove 18 is greater than the protrusion separation distance a. The width b of the groove 18 is the separation distance in the axial direction X between a row of protrusions 16 which extends in the direction different from the axial direction X and a row of protrusions 16 which is parallel thereto.

According to the paper feed roller 10 described above, the grooves 18 which are continuous recesses are formed on the circumferential surface of the elastic body layer 14 in the direction different from the axial direction X by the rows of the protrusions 16 which are arranged on the circumferential surface of the elastic body layer 14 in the direction different from the axial direction X and the rows of the protrusions 16 which are parallel thereto, the widths of the grooves 18 are greater than the protrusion separation distance a in the row of the protrusions 16 which are arranged in the direction different from the axial direction X, and therefore, paper sheet transport failure caused by accumulation of paper powder is prevented for a long period of time. The reason for this is that paper powder generated on the protrusions 16, which serve as contact surfaces with paper sheets at the time of paper feed, is allowed to easily escape to the neighboring grooves 18 from the protrusions 16 since the widths of the grooves 18 are greater than the protrusion separation distance a in the rows of the protrusions 16 which are arranged in the direction different from the axial direction X, and paper powder is easily discharged to the outside of the roller from the grooves 18 according to rotation of the roller without staying in the grooves 18 since the grooves 18 are continuous in the direction different from the axial direction X. In addition, since the grooves 18 of the continuous recesses are formed in the direction at the predetermined angle θ with respect to the circumferential direction Y in the paper feed roller 10, paper powder generated on the protrusions 16 is allowed to easily escape to the neighboring grooves 18 from the protrusions 16. In addition, since the protrusions 16 have hemispherical shapes and the contact surfaces with paper sheets are curved surfaces, the generation of paper powder is relatively suppressed, which improves paper feed performance.

For the rows of the protrusions 16 in the direction different from the axial direction X, the angle θ in an exemplary embodiment is in a range of +10° with respect to the circumferential direction Y. That is, the protrusions 16 in an exemplary embodiment are arranged on the circumferential surface of the elastic body layer 14 in the direction at an angle of +10° with respect to the circumferential direction Y. As described above, forming the grooves 18 which are continuous recesses in the direction at the predetermined angle θ with respect to the circumferential direction Y makes it easier for paper powder generated on the protrusions 16 to escape from the protrusions 16 to the neighboring groove 18. On the other hand, if the angle θ is too large, paper powder moved to the grooves 18 may easily accumulate at corners of the grooves 18. Therefore, the angle θ in an exemplary embodiment is in the range of +10° with respect to the circumferential direction Y in view of easy discharge of paper powder from the grooves 18 to the outside of the roller.

The protrusion separation distance a in an exemplary embodiment is in a range of 0 to 0.6 mm. If the protrusion separation distance a is 0.6 mm or less, paper powder does not easily stay in the gaps between the rows of protrusions 16, the paper powder easily moves to the neighboring grooves 18, and thus the paper powder is easily discharged to the grooves 18. In addition, since the number of protrusions 16 in the direction of the row of the protrusions 16 is large, the area of the contact surfaces with a paper sheet increases, a load on the paper sheet is suppressed to a low level, and thus generation of paper powder is easily suppressed. In view of this, the protrusion separation distance a in an exemplary embodiment is 0.5 mm or less, and is 0.4 mm or less in another exemplary embodiment.

The width b of the groove 18 in an exemplary embodiment is in a range of 0.01 to 2.0 mm. If the width b of the groove 18 is 0.01 mm or more, paper powder moved to the grooves 18 does not easily clogged in the grooves 18 but is easily discharged from the grooves 18 to the outside of the roller. In view of this, the width b of the groove 18 in an exemplary embodiment is 0.05 mm or more and is 0.1 mm or more in another exemplary embodiment. In addition, if the width b of the groove 18 is 2.0 mm or less, a contact area with the paper sheet increases since the number of the protrusions 16 in the axial direction X is large, a load on the paper sheet is suppressed to a low level, and thus generation of paper powder is easily suppressed. In view of this, the width b of the groove 18 in an exemplary embodiment is 1.8 mm or less and is 1.5 mm or less in another exemplary embodiment.

A height h of the protrusions 16 in an exemplary embodiment is in a range of 0.05 to 0.5 mm. If the height h of the protrusions 16 is 0.05 mm or more, the volume of the grooves 18 increases, and paper powder moved to the grooves 18 is not easily clogged in the grooves 18, and is easily discharged from the grooves 18 to the outside of the roller. In view of this, the height h of the protrusions 16 in an exemplary embodiment is 0.1 mm or more. In addition, if the height h of the protrusions 16 is 0.5 mm or less, a size r′ of the protrusion 16 is suppressed to be reasonably small, and thus a movement distance of paper powder to the grooves 18 is suppressed to be short, and the paper powder is easily discharged to the grooves 18. In view of this, the height h of the protrusions 16 in an exemplary embodiment is 0.3 mm or less.

A curvature radius r of the protrusions 16 in an exemplary embodiment is in a range of 0.05 to 1.0 mm. If the curvature radius of the protrusion 16 is 0.05 mm or more, a contact area with paper increases, a load on the paper is suppressed to a low level, and generation of paper powder is easily suppressed. In view of this, the curvature radius r of the protrusion 16 in an exemplary embodiment is 0.10 mm or more. In addition, if the curvature radius r of the protrusion 16 is 1.0 mm or less, the size r′ of the protrusion 16 is suppressed to be reasonably small, and thus a movement distance of paper powder to the grooves 18 is suppressed to be short, and the paper powder is easily discharged to the grooves 18. In view of this, the curvature radius r of the protrusion 16 in an exemplary embodiment is 0.8 mm or less.

The size r′ of the protrusion 16 is expressed as a maximum diameter of the protrusion 16. The size r′ of the protrusion 16 is determined by the height h of the protrusion 16 and the curvature radius r of the protrusion 16. To set the size r′ of the protrusion 16 to a predetermined size, the height h of the protrusion 16 and the curvature radius r of the protrusion 16 may be adjusted. The size r′ of the protrusion 16 in an exemplary embodiment is in a range of 0.10 to 1.73 mm. If the size r′ of the protrusion 16 is 0.10 mm or more, a contact area with a paper sheet increases, a load on the paper sheet is suppressed to a low level, and generation of paper powder is easily suppressed. In view of this, the size r′ of the protrusion 16 in an exemplary embodiment is 0.20 mm or more. In addition, if the size r′ of the protrusion 16 is 1.73 mm or less, a movement distance of paper powder to the grooves 18 is suppressed to be short, and the paper powder is easily discharged to the grooves 18. In view of this, the size r′ of the protrusion 16 in an exemplary embodiment is 1.30 mm or less.

If the height h and the curvature radius r of the protrusion 16 have the relationship of h=r, the protrusion 16 has the shape of a half of a sphere cut on a plane passing through the center of the sphere as illustrated in FIG. 3 (a). On the other hand, if h<r is satisfied, the protrusion 16 has a shape smaller than a half of a sphere as illustrated in FIG. 3 (b). Since the shape illustrated in FIG. 3 (b) has a gentler angle of a tangent 1, paper powder easily moves from the protrusion 16 to the grooves 18 and thus the paper powder is easily discharged to the grooves 18. In view of this, the height h and the curvature radius r of the protrusion 16 in an exemplary embodiment have the relationship of h<r. In addition, h<(½)×r is particularly preferable.

A pitch p of the grooves 18 is determined by the size r′ of the protrusion 16 (the curvature radius r of the protrusion 16 and the height h of the protrusion 16) and the width b of the groove 18. The pitch p of the grooves 18 may be appropriately determined according to these factors. The pitch p of the grooves 18 in an exemplary embodiment is in a range of 0.1 to 2.0 mm. If the pitch p of the grooves 18 is 0.1 mm or more, the width of the grooves 18 increases, and thus paper powder moved to the grooves 18 does not easily clogged in the grooves 18 but is easily discharged from the grooves 18 to the outside of the roller. In view of this, the pitch p of the grooves 18 in an exemplary embodiment is 0.3 mm or more. In addition, if the pitch p of the grooves 18 is 2.0 mm or less, the size r′ of the protrusion 16 is suppressed to be reasonably small, and thus a movement distance of paper powder to the grooves 18 is suppressed to be short, and the paper powder is easily discharged to the grooves 18. In view of this, the pitch p of the grooves 18 in an exemplary embodiment is 1.8 mm or less.

An arrangement angle θ of the protrusions 16, the protrusion separation distance a, the width b of the grooves 18, the height h of the protrusions 16, the curvature radius r of the protrusions 16, the size r′ of the protrusions 16, and the pitch p of the grooves 18 can be obtained by analyzing a surface photo and an axial cross-section photo of the elastic body layer 14.

The paper feed roller according to the disclosure is not limited to the above-described embodiment. Although the hemispherical protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in the spiral shape in the direction at the predetermined angle θ with respect to the circumferential direction Y in the above-described embodiment, for example, a plurality of rows of the protrusions 16 circling in the direction at the predetermined angle θ with respect to the circumferential direction Y may be arranged on the circumferential surface of the elastic body layer 14, rather than in the spiral shape.

In addition, although the protrusions 16 are hemispherical in the above-described embodiment, for example, a shape in which the base widens is possible as long as it has a curved surface.

In addition, the paper feed roller according to the present embodiment may be configured like a paper feed roller 20 illustrated in FIG. 4. The paper feed roller 20 illustrated in FIG. 4 has a difference in the arrangement of protrusions 16 from the paper feed roller 10 illustrated in FIG. 1. Since other configurations are similar to those of the paper feed roller 10 illustrated in FIG. 1, description thereof will not be repeated.

In the paper feed roller 20 illustrated in FIG. 4, the protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in a direction different from the axial direction X. Specifically, the protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in the circumferential direction Y. Further, although the protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in the axial direction X as well, the protrusions 16 may not be arranged in the axial direction X.

In rows of the protrusions 16 in the circumferential direction Y, the protrusions 16 are separated from one another by predetermined gaps in the row. Grooves 18 that are continuous recesses are formed between rows of the protrusions 16 which extend in the circumferential direction Y and row of protrusions 16 which is parallel thereto. A width of the groove 18 is greater than a separation distance of the protrusions 16. The width of the groove 18 is the separation distance in the axial direction X between a row of protrusions 16 that extends in the circumferential direction Y and a row of protrusions 16 which is parallel thereto.

According to the paper feed roller 20 as described above, the grooves 18 which are continuous recesses are formed on the circumferential surface of the elastic body layer 14 in the circumferential direction Y by the rows of the protrusions 16 which are arranged on the circumferential surface of the elastic body layer 14 in the circumferential direction Y and the rows of the protrusions 16 which are parallel thereto, the widths of the grooves 18 are greater than the protrusion separation distance in the rows of the protrusions 16 which are arranged in the circumferential direction Y, and therefore paper sheet transport failure caused by accumulation of paper powder is prevented for a long period of time. The reason for this is that paper powder generated on the protrusions 16, which serve as contact surfaces with paper sheets at the time of paper feed, is allowed to easily escape to the neighboring grooves 18 from the protrusions 16 since the widths of the grooves 18 are greater than the protrusion separation distance in the rows of the protrusions 16 which are arranged in the circumferential direction Y, and paper powder is easily discharged to the outside of the roller from the grooves 18 according to rotation of the roller without staying in the grooves 18 since the grooves 18 are continuous in the circumferential direction Y.

Also for the paper feed roller 20 illustrated in FIG. 4, a protrusion separation distance, a width of the grooves 18, a height of the protrusions 16, a curvature radius of the protrusions 16, a pitch of the grooves 18, and the like may be set, similarly to the protrusion separation distance a, the width b of the grooves 18, the height h of the protrusions 16, the curvature radius r of the protrusions 16, the pitch p of the grooves 18, and the like of the paper feed roller 10 illustrated in FIG. 1.

In addition, although the protrusions 16 are hemispherical in the above-described embodiment, the protrusions 16 may have a spherical segment shape. FIG. 5 illustrates a paper feed roller according to another embodiment of the disclosure. FIGS. 6 and 7 illustrate an example of a cross-sectional shape of a spherical segment-shaped protrusion. The paper feed roller 30 illustrated in FIG. 5 has a difference in the shape of the protrusions 16 from the paper feed roller 10 illustrated in FIG. 1. Since other configurations are similar to those of the paper feed roller 10 illustrated in FIG. 1, description thereof will not be repeated.

The protrusions 16 are spherical segment-shaped protrusions as illustrated in FIG. 6. When a spherical surface crosses two parallel planes, the part of the spherical surface sandwiched by the two planes is a spherical zone, and the solid surrounded by the spherical zone and the two planes is a spherical segment. That is, the spherical segment-shaped protrusion is a protrusion 16 formed of a solid surrounded by the spherical zone 16 a and the two planes (an upper bottom 16 b and a lower bottom 16 c). The upper bottom 16 b is a surface visible on the outside and serves as a contact surface with a paper sheet. The lower bottom 16 c is a surface integrated with the circumferential surface of the elastic body layer 14. A spherical surface is a substantially spherical surface, and a spherical surface in a shape close to a sphere having a curved surface is applicable. Spherical shapes include, for example, a true spherical shape and an elliptically spherical shape. One of the two planes of the spherical segment may be a plane passing through the center of the sphere or both the two planes of the spherical segment may be planes not passing through the center of the sphere. The two planes of the spherical segment may be surfaces close to planes, and for example, may be curved surfaces having a larger curvature radius than the spherical zone. That is, the upper bottom 16 b of the spherical segment-shaped protrusion 16 may be a plane or a curved surface having a larger curvature radius than the spherical zone. In addition, the upper bottom 16 b of the protrusion 16 may be a polished surface k as illustrated in FIG. 7. The polished surface k can be formed by polishing the upper bottom 16 b of the protrusion 16.

According to the paper feed roller 30 described above, since the protrusions 16 provided on the circumferential surface of the elastic body layer 14 are spherical segment-shaped protrusions, generation of paper powder is suppressed, and paper sheet transport failure is prevented for a long period of time. A reason for this is that, since the spherical zone 16 a of the protrusion 16 is curved surface projecting upward and the angle α formed by the tangent 1 to the spherical zone 16 a of the protrusion at the intersection point 16 d of the spherical zone with the upper bottom 16 b of the protrusion 16 is gentle at an obtuse angle, a paper surface is hardly caught at the shoulder S that is the intersection point of the upper bottom 16 b with the spherical zone 16 a of the protrusion 16, and a generation amount of paper powder is accordingly suppressed. In addition, another reason is that, since the protrusion 16 has the upper bottom 16 b which is a plane or a curved surface having a larger curvature radius than the spherical zone 16 a, the contact area with a paper sheet at the tip of the protrusion 16 increases, stress is dispersed, a pressing force applied to the paper sheet is suppressed to a low level, and a generation amount of paper powder is accordingly suppressed. When the upper bottom 16 b of the protrusion 16 is the polished surface k, generation of paper powder is particularly suppressed.

A diameter of the lower bottom 16 c of the spherical segment-shaped protrusion 16 in an exemplary embodiment is larger than that of the upper bottom 16 b. In addition, a proportion of a diameter r1 of the upper bottom 16 b to a diameter r2 of the lower bottom 16 c (r1/r2) in an exemplary embodiment is in a range of 0.50 to 0.95. If r1/r2 is 0.50 or more, an area of the upper bottom 16 b in contact with a paper sheet increases, stress is dispersed, a pressing force applied to the paper sheet is suppressed to a low level, and a generation amount of paper powder is easily suppressed to be small accordingly. In view of this, r1/r2 in an exemplary embodiment is 0.55 or more, and is 0.60 or more in another exemplary embodiment. In addition, if r1/r2 is 0.95 or lower, the angle α formed by the tangent 1 of the spherical zone 16 a at the intersection point 16 d of the spherical zone 16 a with the upper bottom 16 b increases, a paper surface is hardly caught at the shoulder S that is the intersection of the upper bottom 16 b with the spherical zone 16 a, and therefore a generation amount of paper powder is easily suppressed to a low level. In view of this, r1/r2 in an exemplary embodiment is 0.90 or lower, and is 0.85 or lower in another exemplary embodiment.

The angle α formed by the tangent 1 of the spherical zone 16 a of the protrusion 16 at the intersection point 16 d of the spherical zone 16 a with the upper bottom 16 b of the protrusion 16 in an exemplary embodiment is in a range of 100 to 150°. If the formed angle α is 100° or more, a paper surface is hardly caught at the shoulder S that is the intersection of the upper bottom 16 b with the spherical zone 16 a of the protrusion 16, and therefore a generation amount of paper powder is easily suppressed to a low level. In view of this, the formed angle α in an exemplary embodiment is 110° or more, and is 120° or more in another exemplary embodiment. In addition, if the formed angle α is 150° or less, an area of the upper bottom 16 b in contact with a paper sheet increases, thus stress is dispersed, a pressing force applied to the paper sheet is suppressed to a low level, and a generation amount of paper powder is accordingly suppressed to a low level. In view of this, the formed angle α in an exemplary embodiment is 145° or less, and is 140° or less in another exemplary embodiment.

The height h of the protrusion 16 in an exemplary embodiment is in a range of 0.02 to 0.40 mm. If the height h of the protrusion 16 is 0.02 mm or more, the volume of the recess between the protrusions 16 increases, and thus generated paper powder does not easily clogged therein. In view of this, the height h of the protrusion 16 in an exemplary embodiment is 0.05 mm or more. In addition, if the height h of the protrusion 16 is 0.40 mm or less, the diameter r2 of the lower bottom 16 c of the protrusion 16 is suppressed to be reasonably small, thus a dispersion property of the protrusions 16 is improved, and an effect of dispersing pressure to a paper sheet is improved. Accordingly, the generation of paper powder is easily suppressed. In view of this, the height h of the protrusion 16 in an exemplary embodiment is 0.30 mm or less.

The diameter r1 of the upper bottom 16 b of the protrusion 16 in an exemplary embodiment is in a range of 0.095 to 0.50 mm. If the diameter r1 of the upper bottom 16 b is 0.095 mm or more, an area of the upper bottom 16 b in contact with a paper sheet increases, thus stress is dispersed, a pressing force applied to the paper sheet is suppressed to a low level, and thus a generation amount of paper powder is easily suppressed to a low level. In view of this, the diameter r1 of the upper bottom 16 b in an exemplary embodiment is 0.10 mm or more, and is 0.15 mm or more in another exemplary embodiment. In addition, if the diameter r1 of the upper bottom 16 b is 0.50 mm or less, the diameter r2 of the lower bottom 16 c of the protrusion 16 is suppressed to be reasonably small, thus a dispersion property of protrusions 16 is improved, and an effect of dispersing pressure to the paper sheet is improved. Accordingly, generation of paper powder is easily suppressed. In view of this, the diameter r1 of the upper bottom 16 b in an exemplary embodiment is 0.40 mm or less.

The diameter r2 of the lower bottom 16 c of the protrusion 16 in an exemplary embodiment is in a range of 0.10 to 1.00 mm. If the diameter r2 of the lower bottom 16 c is 0.10 mm or more, an area of the upper bottom 16 b in contact with a paper sheet relatively increases, thus stress is dispersed, a pressing force applied to the paper sheet is suppressed to a low level, and thus a generation amount of paper powder is easily suppressed to a low level. In view of this, the diameter r2 of the lower bottom 16 c in an exemplary embodiment is 0.20 mm or more. In addition, if the diameter r2 of the lower bottom 16 c is 1.00 mm or less, the diameter r2 of the lower bottom 16 c of the protrusion 16 is suppressed to be reasonably small, thus a dispersion property of the protrusions 16 is improved, and an effect of dispersing pressure to the paper sheet is improved. Accordingly, generation of paper powder is easily suppressed. In view of this, the diameter r2 of the lower bottom 16 c in an exemplary embodiment is 0.80 mm or less, and is 0.60 mm or less in another exemplary embodiment.

A curvature radius SR of the spherical zone 16 a in an exemplary embodiment is in a range of 0.05 to 0.50 mm. If the curvature radius SR is 0.05 mm or more, the curved surface of the spherical zone 16 a becomes relatively gentle, an area of the upper bottom 16 b in contact with a paper sheet is likely to increase, thus stress is dispersed, a pressing force applied to the paper sheet is suppressed to a low level, and thus a generation amount of paper powder is easily suppressed to a low level. In view of this, the curvature radius SR in an exemplary embodiment is 0.10 mm or more. In addition, if the curvature radius SR is 0.50 mm or less, the diameter r2 of the lower bottom 16 c of the protrusion 16 is suppressed to be reasonably small, thus a dispersion property of protrusions 16 is improved, and an effect of dispersing pressure to the paper sheet is improved. Accordingly, generation of paper powder is easily suppressed. In view of this, the curvature radius SR in an exemplary embodiment is 0.40 mm or less.

The diameter r1 of the upper bottom 16 b, the diameter r2 of the lower bottom 16 c, the curvature radius SR of the spherical zone 16 a, the height h, the formed angle α, and the like of the protrusion 16 can be obtained by analyzing a surface photo and a cross-section photo of the elastic body layer 14.

In the paper feed roller 30 in which the protrusions 16 have a spherical segment shape, although the protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in a spiral shape in a direction at a predetermined angle θ with respect to the circumferential direction Y, similarly to the paper feed roller 10, a plurality of rows of the protrusions 16 circling in the direction at the predetermined angle θ with respect to the circumferential direction Y may be arranged on the circumferential surface of the elastic body layer 14, rather than in the spiral shape.

In addition, although, in the paper feed roller 30 in which the protrusions 16 have a spherical segment shape, the protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 in the spiral shape in the direction at the predetermined angle θ with respect to the circumferential direction Y, also in a paper feed roller in which protrusions 16 have a spherical segment shape as in the paper feed roller 20 illustrated in FIG. 4, the protrusions 16 may be arranged on the circumferential surface of the elastic body layer 14 in the circumferential direction Y. Further, although the protrusions 16 are arranged on the circumferential surface of the elastic body layer 14 also in the axial direction X, the protrusions 16 may not be arranged in the axial direction X.

In rows of protrusions 16 in the circumferential direction Y, the protrusions 16 are separated from one another by predetermined gaps in the row. Grooves 18 that are continuous recesses are formed between rows of protrusions 16 which extend in the circumferential direction Y and rows of protrusions 16 which are parallel thereto. A width of the groove 18 is greater than a separation distance of the protrusions 16. The width of the groove 18 is the separation distance between a row of protrusions 16 that extends in the circumferential direction Y and a row of protrusions 16 which is parallel thereto in the axial direction X.

Also for the paper feed roller in which the protrusions 16 have the spherical segment shape, an angle θ, a protrusion separation distance, a width of the groove 18, a height of the protrusions 16, a pitch of the grooves 18, and the like may be set, similarly to the angle θ, the protrusion separation distance a, the width b of the groove 18, the pitch p of the grooves 18, and the like of the paper feed roller 10 in which the protrusions 16 have the hemispherical shape.

Next, a material composition of a paper feed roller according to the disclosure will be described.

For the shaft body 12, a core bar formed of a metal solid body, a metal cylindrical body of which the inside is hollowed out, or the like may be used. In addition, examples of a material thereof include stainless steel, aluminum, plated iron, and the like. Further, an adhesive, a primer, or the like may be applied onto the shaft body 12 if necessary, and the adhesive, the primer, or the like may be made conductive if necessary.

The elastic body layer 14 may be formed of an elastic material such as a rubber cross-linking substance. A material thereof is not particularly limited as long as it is a rubber-like elastic material. A known rubber material, for example, urethane rubber, hydrin rubber, silicone rubber, and the like can be used.

The elastic body layer 14 in an exemplary embodiment is conductive or semi-conductive. Specifically, a volume resistivity of the elastic body layer 14 in an exemplary embodiment is in a range of 10² to 10¹⁰ Ω·cm, 10³ to 10⁹ Ω·cm, and 10⁴ to 108 Ω·cm. If the elastic body layer 14 is conductive or semi-conductive, residual charge on a surface of the elastic body layer 14 is suppressed to a low level, and thus adhesion of paper powder is easily prevented.

The elastic body layer 14 may include a conductive agent in view of a low electrical resistance. Examples of conductive agent include electronic conductive agent and an ion conductive agent. Examples of electronic conductive agent include carbon black, graphite, c-TiO₂, c-ZnO, c-SnO₂ (c—means conductivity), and the like. Examples of ion conductive agent include a quaternary ammonium salt, a borate, a surfactant, and the like.

The elastic body layer 14 may have any of various additives appropriately added thereto if necessary. Examples of additives include a lubricant, a vulcanization accelerator, an anti-aging agent, a light stabilizer, a viscosity modifier, a processing aid, a flame retardant, a plasticizer, a filler, a dispersant, an antifoaming agent, a pigment, a release agent, and the like.

A thickness of the elastic body layer 14 is not particularly limited and may be appropriately set in a range of 0.1 to 10 mm or the like.

The elastic body layer 14 can be formed by molding with a molding die using a rubber composition, or the like. The elastic body layer 14 can be formed on an outer periphery of the shaft body 12, for example, by installing the shaft body 12 coaxially with a hollow part of a roller molding die, injecting an uncrosslinked rubber composition, and performing heating, curing (crosslinking), and then demolding, and the like. A molding die in which recesses in a shape corresponding to the protrusions 16 are formed on the circumferential surface can be used. The protrusions 16 of the elastic body layer 14 can be formed, for example, by mold transfer using a molding die.

EXAMPLES

The disclosure will be described in detail using Examples and Comparative examples below.

Examples 1 to 18 and Comparative Examples 1 to 4

Elastic body layers (having a thickness of 3 mm) formed of a urethane rubber composition were formed on outer peripheries of core materials (having φ6 made of SUS 304) using cylindrical molding dies having predetermined recesses on the inner circumferential surfaces. Accordingly, paper feed rollers having the surface shape as illustrated in FIG. 4 or FIG. 1 were obtained. In other words, unevenness were formed by the hemispherical protrusions on the circumferential surfaces of the elastic body layers. In Example 1 and Comparative example 1, the hemispherical protrusions were arranged to circle around the circumferential surface of the elastic body layer as illustrated in FIG. 4. In other Examples and Comparative examples, the hemispherical protrusions were arranged on the circumferential surface of the elastic body layer in a spiral shape as illustrated in FIG. 1. Then, grooves that are continuous recesses were formed on the circumferential surface of the elastic body layer by rows of protrusions and rows of protrusions parallel thereto. In each of the paper feed rollers, the dimensions illustrated in FIGS. 2(a) and 2(b) with respect to the hemispherical protrusions (the protrusion separation distance a, the width b of the groove, the height h of the protrusions, the curvature radius r of the protrusion, and the arrangement angle θ of the protrusions) were set as shown in Tables 1 and 2.

Durability was evaluated using the manufactured paper feed rollers. The result is shown in Tables 1 and 2 together with the protrusion separation distance a, the width b of the groove, the height h of the protrusion, the curvature radius r of the protrusion, and the arrangement angle θ of the protrusions.

(Evaluation of Durability)

The paper feed rollers were incorporated into commercially available copiers with a FRR type paper feed system and paper feeding properties were evaluated. Commercially available PCC paper sheets were used as paper sheets, 100,000 sheets were fed, and the number of paper jams was measured. “⊚” indicates no paper jam occurred, “∘” indicates one to three paper jams occurred, “Δ” indicates four to nine paper jams occurred, and “x” indicates ten or more paper jams occurred.

TABLE 1 Examples 1 2 3 4 5 6 7 8 9 10 11 12 Separation distance a (mm) 0.3 0.3 0 0.3 0 0.6 0.3 0.3 0.3 0.3 0.3 0.3 Groove width b (mm) 1.0 1.0 0.01 2.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Protrusion height h (mm) 0.2 0.2 0.2 0.2 0.2 0.2 0.05 0.5 0.05 0.2 0.2 0.2 Protrusion curvature radius 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.05 1.0 0.5 0.5 r (mm) Arrangement angle θ (°) 0 5 5 5 5 5 5 5 5 5 10 −10 Durability ◯ ⊚ Δ ◯ ⊚ ⊚ ◯ ⊚ Δ ⊚ ⊚ ⊚

TABLE 2 Examples Comparative examples 13 14 15 16 17 18 1 2 3 4 Separation 0.7 0.3 0.3 0.3 0.3 0.3 1.0 1.0 1.0 1.0 distance a (mm) Groove 1.0 2.5 1.0 1.0 1.0 1.0 0.5 0.5 0.5 0.5 width b (mm) Protrusion 0.2 0.2 0.01 1.0 0.2 0.2 0.2 0.2 0.2 0.2 height h (mm) Protrusion 0.5 0.5 0.5 2.0 0.5 0.5 0.5 0.5 0.5 0.5 curvature radius r (mm) Arrangement 5 5 5 5 20 −20 0 5 20 −20 angle θ (°) Durability Δ Δ Δ Δ Δ Δ X X X X

According to Comparative examples, the width b of the groove was set to be smaller than the protrusion separation distance a in the row of the protrusions, the number of paper jams occurred due to paper powder was large such as 10 or more, and durability was not satisfactory. On the other hand, according to Examples, the width b of the groove was set to be larger than the protrusion separation distance a in the rows of the protrusions, the number of paper jams occurred due to paper powder was small such as 9 or less, and durability was satisfactory.

In addition, it is ascertained in Examples that the number of paper jams occurred was further reduced when the angle θ was ±10° or less. In addition, it is ascertained that the number of paper jams occurred was reduced more when the angle θ was 5° than when it was 0°. In addition, it is ascertained that the number of paper jams occurred was reduced more when the protrusion separation distance a was 0.6 mm or less, the width b of the groove was 2.0 mm or less and 1.5 mm or less, and the height h of the protrusion was 0.05 to 0.5 mm.

Example 19

A paper feed roller was obtained in a similar way to Example 2 except that the spherical segment-shaped protrusions illustrated in FIG. 7 were employed instead of the hemispherical protrusions. The upper bottoms of the spherical segment-shaped protrusions were set to be polished surfaces. The spherical segment-shaped protrusions were arranged on the circumferential surface of the elastic body layer in a spiral shape. In addition, the grooves that are continuous recesses were formed on the circumferential surface of the elastic body layer by rows of protrusions and rows of protrusions parallel thereto. The dimensions were set as follows.

Protrusion separation distance a: 0.3 mm

Width b of each groove: 1.0 mm

Arrangement angle θ of protrusions: 5°

Example 20

A paper feed roller was obtained in a similar way to Example 2 except that the spherical segment-shaped protrusions illustrated in FIG. 6 were employed instead of the hemispherical protrusions. The upper bottoms of the spherical segment-shaped protrusions were set to be planes. The spherical segment-shaped protrusions were arranged on the circumferential surface of the elastic body layer in a spiral shape. In addition, the grooves that are continuous recesses were formed on the circumferential surface of the elastic body layer by rows of protrusions and rows of protrusions parallel thereto. The dimensions were set as follows.

Protrusion separation distance a: 0.3 mm

Width b of grooves: 1.0 mm

Arrangement angle θ of protrusions: 5°

Measurement of the amounts of paper powder generated and evaluation of durability were performed with respect to the paper feed rollers manufactured in Examples 19 and 20. The results are shown in Table 3 together with the configuration of the protrusions.

(Paper Powder Generation Amount)

The paper feed rollers were incorporated into commercially available copiers with a FRR type paper feed system, commercially available PCC paper sheets were used to feed 100,000 sheets, then tape of a predetermined area was attached to the roller surfaces to transfer paper powder on the roller surfaces to the tape, and the difference in the tape weights before and after the transfer was measured. The paper powder generation amount of each paper feed roller was expressed by a relative proportion when the paper powder generation amount of Example 1 was set to 1. “⊚” indicates the case in which the proportion is lower than 1.0, “∘” indicates the case in which the proportion is 1.0 or more and lower than 1.2, “Δ” indicates the case in which the proportion is 1.2 or more and lower than 2.0, and “x” indicates the case in which the proportion is 2.0 or more.

(Evaluation of Durability)

The result is as described above.

TABLE 3 Examples 19 20 Protrusion Protrusion shape Spherical segment Spherical configuration segment Upper bottom shape Polished surface Plane Upper bottom polishing Applied Not applied Spherical zone SR (mm) 0.20 0.20 Upper bottom diameter 0.30 0.30 r1 (mm) Lower bottom diameter 0.40 0.40 r2 (mm) Protrusion height h (mm) 0.13 0.13 Shoulder angle α (°) 131 131 r1/r2 0.75 0.75 Protrusion arrangement Applied Applied Evaluation Paper powder ⊚ Δ suppression Durability ⊚ ◯

According to Examples 19 and 20, it is ascertained that, since the protrusions formed on the circumferential surfaces of the elastic body layers had a spherical segment shape, the generation of paper powder was suppressed and durability was improved. In addition, it is ascertained from Examples 19 that providing the polished surfaces on the upper bottoms of the spherical segment-shaped protrusions helped the generation of paper powder suppressed.

Although the embodiments and examples of the disclosure have been described above, the disclosure is not limited at all to the embodiments and examples, and can be variously modified within the scope not departing from the gist of the disclosure. 

1. A paper feed roller comprising: a shaft body; and an elastic body layer formed on an outer periphery of the shaft body, wherein unevenness are formed by protrusions on a circumferential surface of the elastic body layer, and the protrusions are hemispherical protrusions, wherein the protrusions are arranged on the circumferential surface of the elastic body layer in a direction different from a circumferential direction in an angle of ±10° or less with respect to the circumferential direction, and grooves that are continuous recesses are formed between rows of protrusions that extend in the direction different from the circumferential direction in the angle of ±10° or less with respect to the circumferential direction and rows of protrusions that are parallel to the rows of the protrusions, the protrusions are arranged on the circumferential surface of the elastic body layer in a spiral shape, a width of one of the grooves is larger than a protrusion separation distance in one row of protrusions, and the protrusion separation distance in the row of protrusions is in a range of 0 to 0.6 mm the width of one of the grooves is in a range of 0.01 to 2.0 mm, a height of one of the protrusions is in a range of 0.05 to 0.5 mm, a curvature radius of one of the protrusions is in a range of 0.05 to 1.0 mm, and a pitch of the grooves is in a range of 0.1 to 2.0 mm. 